Is the water in Grand Lake too murky? |

Is the water in Grand Lake too murky?

A local advocacy group has renewed longstanding questions about how pumping water from Grand County to the Front Range disrupts Colorado’s largest and deepest natural lake

Chris Outcalt
The Colorado Sun
A bridge over the waterway that connects between Grand Lake and Shadow Mountain Reservoir on Sept. 19, 2022, near the town of Grand Lake.
Hugh Carey/The Colorado Sun

Zipping across Grand Lake in an outboard motorboat on a warm day in late September, Mike Cassio eases off the throttle as he nears a break in the shoreline and points out one of two tributaries that feed Colorado’s largest and deepest natural body of water. This one is called the North Inlet. It winds about a dozen miles northeast into Rocky Mountain National Park. “If you go up here,” Cassio says, “this river is pristine. It’s unreal how beautiful and clear that is.”

This is how Mother Nature drew it up. A natural lake, left behind by a receding glacier, perched at 8,369 feet, framed just so by some of Colorado’s most prized wilderness. However, a remarkable feat of engineering, the Colorado-Big Thompson project, disrupted the balance of this ecological system. A massive federal Bureau of Reclamation project that moves water from the Colorado River headwaters in Grand County to the northern Front Range, C-BT supplies drinking water to more than a million Coloradans and supplemental irrigation to 615,000 acres of farmland. 

Getting this critical water to communities on the northern Front Range impacts communities on this side of the mountains. One of the characteristics of the C-BT system that has frustrated Grand Lake residents from just about the moment the bureau completed the project in 1956 is that C-BT at times operates by pushing murkier water marred by weeds and algae into Grand Lake, turning, as locals describe it, what would otherwise be a pristine mountain pool into something that more resembles a bowl of split pea soup. 

Locals consider the clarity of this lake an important community asset, something to be enjoyed not just by those who live here but everyone who comes to visit. What’s more, they contend that as long as people have thought about the significance of this plumbing project there were also those who recognized the value of a crystal clear Grand Lake and sought to protect the water. 

For years, multiple agencies have worked on addressing the clarity in Grand Lake, and, by some measures, it has improved. This summer, however, the Three Lakes Watershed Association brought new attention to the issue when it presented to the state legislature’s Interim Water Resources and Agricultural Review Committee. The association asked the state to independently review not just the clarity in Grand Lake but also whether the entire Western Slope C-BT system might be in need of a facelift. “The system was designed in 1937,” Cassio said. “It’s old and needs an update.”


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